/Engine/Source/Runtime/Engine/Public/AnimationRuntime.h
Convert TargetPose into an AdditivePose, by doing TargetPose = TargetPose - BasePose
static void ConvertPoseToAdditive ( [FCompactPose](API\Runtime\Engine\FCompactPose) & TargetPose, const [FCompactPose](API\Runtime\Engine\FCompactPose) & BasePose )